1. Field of the Invention
The present invention relates to an imaging device that reduces fixed pattern noise from captured image data.
The present invention also relates to an imaging device that records information on the fixed pattern noise together with the image data and to an image processing program for reducing the fixed pattern noise from the image data by computer processing.
2. Description of the Related Art
Image quality of an imaging device is generally lowered when fixed pattern noise is superimposed on image data. A conventional method improves the image quality by storing the fixed pattern noise for one screen read from an image sensor and eliminating the fixed pattern noise for one screen from the image data by common mode rejection.
In particular, Japanese Unexamined Patent Application Publication No. Hei 7-15632 (hereinafter, referred to as “patent document 1”) discloses a technique of obtaining fixed pattern noise with random noise being reduced therefrom, by reading and averaging fixed pattern noise for a plurality of screens.
In order to read the aforesaid fixed pattern noise from the image sensor, it takes the same length of time as it normally takes to read an image. This causes a problem in continuous shooting that the speed of continuous shooting is lowered by the time corresponding to this read time of the fixed pattern noise. Especially in the case of the patent document 1, the delay of the continuous shooting speed is prominent since the fixed pattern noise for the plural screens has to be read.
Further, the read fixed pattern noise occupies a space corresponding to one screen to several screens in a buffer memory in an electronic camera. Accordingly, the buffer memory becomes fully occupied in a short time, causing the delay of the continuous shooting speed.
Due to such double causes, the elimination of the fixed pattern noise leads to a problem of noticeably lowering the speed of the continuous shooting of an electronic camera.
Meanwhile, in the case of eliminating the fixed pattern noise with a computer or the like at a later time, the fixed pattern noise for one screen has to be stored in addition to captured images in an image recording medium (a memory card or the like), which will accordingly cause a problem of reduction in the number of frames recordable in the memory card or the like.